Gyroscope drift compensating means



June 14, 1960 W. B. HANSEL ET AL GYROSCOPE DRIFT COMPENSATING MEANS Original Filed Feb, 16, 1956 FlG. BY

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5 Sheets-Sheet 1 INVENTORS WILLIAM B. HANSEL 8| EINAR T. YOUNG ATTORNEYS June 14, 1960 w. B. HANSEL ET AL 2,940,320

GYROSCOPE DRIFT COMPENSATING MEANS Original Filed Feb. 16, 1956 3 Sheets-Sheet 2 m f Tl a s- 1 a 2 92 4s I a -ao E48 as as 2v |7.4 46 4 m J F.

Fl G. 3.

INVENTORS WILLIAM B. HANSEL & EINAR T; vouue ATTORNEYS June 14, 1960 w. B. HANSEL ET AL 2,940,320

GYROSCOPE DRIFT COMPENSATING MEANS 3 Sheets-Sheet 3 Original Filed Feb. 16, 1956 FIG. 5.

I32 so INVENTORS WILLIAM B. HANSEL 8 EINAR T. YOUNG BY E FIG. 4.

ATTORNEYS United States Patent GYROSCOPE DRIFT COMPENSATING MEANS William B. Hansel, Brookhaven, and Einar T. Young, Newtown Square, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New .lersey Original application Feb. 16, 1956, Ser. No. 565,948. and this application Oct. 22, 1958, Ser. No.

3 Claims. (Cl. 74-5.4)

This invention relates to an odograph for the automatic plotting of the path traversed by a vehicle and has particular reference to the provision of an odograph having an extremely high degree of accuracy.

This application is filed as a division of my copending application, Serial No. 565,948, filed February 16, 1956.

Many proposals have been made in the past for the construction of odographs for the automatic plotting of paths traversed by a supporting vehicle. In general, these have involved charts arranged to be driven in proportion to the linear advance of the carrying vehicle, together with provision of orienting means, such as a gyroscope or magnetic compass follower for establishing an azimuthal reference. However, these proposals have failed to achieve a high degree of plotting accuracy due primarily to reaction of the apparatus on the azimuthal reference means, such as a gyroscope, and effect of inertia producing a departure from the theoretical condition of a rolling contact occurring without relative sliding movement. It is the general object of the present invention to provide an odograph having the parts so arranged as to minimize the disturbing matters just indicated. Specifically, using a gyroscope for azimuthal reference, disturbing loads on the gyroscope are minimized so that the gyroscope will accurately maintain its azimuthal reference, or, as is usually the case, if it drifts the drift will be uniform and therefore correctible. Further, in accordance with the invention, balancing against inertial forces is achieved so as to secure an adequate approximation to a rolling contact, without relative sliding, between a driving roller and a drum or other element on which plotting is effected.

The foregoing and other objects particularly relating to details of construction and operation will become apparent from the following description read in conjunction with the accompanying drawings in which:

Figure 1 is a diagrammatic sectional view showing the lower portion of an odograph provided in accordance with the present invention;

Figure 2 is a continuation of the upper portion of Figure 1;

Figure 3 is a plan view showing, in particular, the association of a stylus with a record drum;

Figure 4 is a sectional view showing details of the stylus mounting and adjusting means;

Figure 5 is a diagrammatic perspective view showing means for making correction for slope of the roadway so as to provide a plot of the vertical projection of the traversed path; and

Figure 6 is adiagram illustrating means desirably employed for gyroscope drift correction.

Referring first to Figure 1, there is indicated at 2 a supporting frame arranged to be secured to the vehicle mounting the odograph. The vehicle may be a power driven one, or may be a trailer, depending upon the use to which the invention is put. Desirably the odograph assembly is mounted to maintain a definite position relative to the horizontal, particularly in view of the use of 2,940,320 Patent d June 1-4, 1960 ice a gyroscope for maintaining azimuthal reference, and accordingly a gimbal 6 is mounted on trunnions sup-- ported by bearings 4 and in the gimbal 6 there is supported, by trunnions defining an axis perpendicular to that defined by the first mentioned trunnions, a frame 8 which supports the odograph assembly proper.

A gyroscope of conventional type is mounted in theframe 3 and is indicated at 10. Mounting of the gyro-- scope rotor is efiected in the usual fashion by gimbals, and the vertical output shaft which is desirably maintained in fixed azimuthal position is indicated at 12. Theoretically, this shaft should maintain a fixed position, but, practically, it will be subject to drift, and either the final plot will be corrected for such drift, or the drift will be compensated in some fashion which forms no part of the present invention. So far as the present invention is concerned, however, provision is made for avoiding, as far as possible, load on the shaft 12. Loading of the shaft 12 would have a deleterious effect in producing drift and, particularly, irregular drift, since any appreciable loading which might occur would be usually varied by inertial forces rseulting from irregularities in the roadway traversed which would set up vi brations of irregular type in the system. In accordance with the present invention, the shaft 12 is required to exert a minimum of effort and in turn is subjected to a minimum of forces which might arise due to inertial disturbances. For this purpose, it is coupled by means of a coupling arrangement indicated at 14 to a shaft 16 which is mounted securely in anti-friction bearings 18 and 20 supported by a fixed member 22 of the support 8- The coupling 14 is so arranged, by a splined pin and slot type of connection, so that axial movements of the shaft 16 are not imparted to the gyroscope output shaft 12. Axial loading of the shaft 12 is thus prevented and the shaft 12 is used only to restrain against rotational movements about a vertical axis a relatively light assemblage of elements. As will appear these elements are subject only to very small torques about. the vertical axis.

A spring 24 urges the shaft 16 upwardly and with it the mounting plate 26 which supports a pair of servo motors 28 and 32 which may convenientlybe of the selsyn type. The output shaft 30 of the servo motors 28 and 32 drives through a worm and wheel arrangement 34, 36 and gearing 38 a drive roller 40 which is urged by the spring 24 into contact with a drum. The drive roller desirably has a spherical driving periphery to provide a good approximation to a point contact between the roller and the cylindrical surface of the drum. The use of two servo motors not only effects balance of inertial forces but also makes possible the use of two small motors rather than a single larger one which, in any event, would require counterbalancing. The torque required from the motors is so small that amplification at their inputs is unnecessary.

The shaft 16 carries a series of slip rings 42 through which current is supplied to the servo motors 28 and 32 through brushes indicated at 44.

Mounted about a horizontal axis in the frame 8 by means of bearings indicated at 48 there is a sleeve member 46 on which there is mounted for axial movement a chart-carrying drum 50 by means of a series of antifrlction rollers 52. The drum 50 mounts the cylindrical paper chart 54 by means of a clamping means indicated at 56, the paper chart being secured thereon over a portion of the drum periphery which in operation is not en gaged by the roller 40. Mounted to slide axially in the sleeve 46 is a roller-supported counterweight 58 which is connected by cables 60 and 62 passing about pulleys 64 and 66 mounted in the sleeve to the anchorages 6S and 70 adjust-ably secured within the drum 50. As will be evident from the arrangement shown, if the drum amaz moves to the right as indicated in Figure 2, the counterweight 58 will move correspondingly to theleft. The result is not only maintenance of balance about all horiings 48 so as to be. restrained against axial movement relative to the frame. 8, it will be evident that, if the counterweight :8 has the same mass as the drum 5i? and the parts carried thereby, such axial accelerations cannot produce any movements ofthe drum in view of: the compensation afforded by the counterweight 58; Accordingly there can'be no slippage, due .to inertial forces, between thedrum'SO and the driving roller -40. I

Substantially-diametrically opposite the point'of contact of the roller 40 withflthe drum "59 there is located the marking stylus 72 mounted in an adjustable slide 74 and .urgedinto'contact with the chart 54 by means of a spring 76. 'Themember 74 is provided with a rack 73 whichris slidably mounted in'a .crosshead 80 which is adjustable along tracks 82 and 84 secured to the frame 8 by means 'of a screw .86 whichlmay be adjusted :by .its spindle'iextensi'on 88. The rack 78 is engageable by a pinion 90 of .elongated'form as will be clear from Fig ure 3, the pinion fl-being adjustable through the gearing a'rrangementindicated at 2 and 94 from a spindle 9 6. lhe'arrangement just described 'provides acljustment in rectangular coordinate directions of the stylus 72 with respect to the chartfl54. 7 These adjustments are provided for the convenient setting of the stylus in definite starting position with respectto the chart 54. It'may beassurned, for purpose of description, that the contact of stylus '72 with the chart is essentially in vertical alignment with the point ofcontactof roller :40 withthe drum. It will lbe'evidenty-however, this-need not -'be strictly true consistent with the plotting of the proper pathof movement of the vehicle.

Drive oftheservo motors 28 and '32, and consequent- 1y of-the roller 40,is desirably -eifected,-with compensati'on for the inclination of=the roadway, by'an arrangement such as diagrammedlin Figure-5. The wheel 95, of definitecircumfer ence, is arranged to engage the --roadway and drives through any suitable connections,.such as indicated at 100 as a flexible shafg a disc 192. A slide-104 mounted forilmovement relative to the-vehicle "in a vertical directionwhenthe vehicle is horizontal is provided-with aplate 106 engaging under downward acti n ofa spring (not 'shown) a ball 168 carried by the upper end'of a pendulum 110 supported by'a fixed pivot 112 for "oscillation in the'plane vertically entending along the axis ofidirection of movement of the vehicle. Af'pair of balls 116 mounted in-the slide 104 are tightly engaged 1 between the disc 102 and a cylinder 11% the axis of which is paralleltothedirectionof sliding movement of'the slide 104. The cylinder '11s in turn drives the servotransmitter 120, which may be-a-selsyn transmitter, and which provides current output through 182165 122 to the brushes 44 to provide driving currentlto I the servo motors 2,3 and 32. The arrangement illustratedin Figure' S isnot part of the present invention, but as willbe obvious, providesa correctionof the drive imparted from wheel 98 to the transmitter IZO- in-accQrd- V about the axis of drum 50land along that axis.

, lever arm of such force is practically zero.

. V a 4 entailing possible components of motion of the chart 54 The movement of the chart relative to the stylus in turn corresponds to this so that there is traced on the chart 54 a map to'reduced scale of the horizontal components of movement of the vehicle. 7 l a The roller 40 is maintained in'tight engagement with the drum Stl by means of the spring 24 fAssumingQno slippage from thesta'ndpoint of rotation of the roller, 9; he m pis i d a i wi e accu at A 'i a by maintenance of a tight contact such slippage Y e avoided. In accordance with the present "inventionffurthermore, slippage due to inential 's'ources is essentially eliminated because of the complete balance of the 50. By reason of its concentric arrangement andbalance about the axis of bearings 48 circumferential slippage between the drum 5% and the roller 49 is eliminated. Sli page in the direction of the axis defined by bearings 48 is avoided :by virtue of the balancing .of the vdrum by means .of the counteriweight .58. High accuracy of mapping due to drive of the drum .by thevroller Minis accordingly secured. r

Furthermore, in view of the minimizing-of forces applied to the shaft ilzlthe 'gyros'cope'isable' to maintain its reference azimuthlto a high degree lfaCQllfilCY ortto a. high degree of correctibility', tl16'idl'ifi,lf any, :heingisubstantially constant. Vertical loading on the shaft 12 is prevented by the splined connection' indicated fatll. Since ,theshaft 16 and all of the parts .carried thereby .are balanced about the vertical axis of the shaft, torques due to inertia are substantially eliminatedfromappliczi: tion to thelshaft 12. Ihe contacts ;of thebrushes 44 with the slip rings 42 may .bernade very light, andisubstantially devoid of frictionlso that frictionaldisturbance due to these is negligible. The only'otherliriction involved is that of the roller .40 againsttlieldrumjil opposing relative turningabout the vertical. axis of shaft 16. However, the contact between roller ilfl-andithe chart is essentially point contact at theaxis of shaftd, and .even though the pressure ,forceexerted between the roller and the chart by spring ,Zimaybefsubstantial,, the Thepresult istaminimum of forces acting inany fasbionzontheshaf 12 so that the gyroscope isv practicallyioperatingntrce of.

restraint or disturbances vso that Jhe azimuth ref-ensue; 'is defined or determinableto a very high degreeot ,ac-

curacy.

lti's desirable in anodograph of the type. described t provide' foricorrection of gyroscope drift: ltfthasbfien found that the drift of a gyroscope inangapparatus of th1s type ,is a function ofarnbient temperature and'will change "throughout a day and it is thcrefflie desirable to provide automatic compensation which will at least minimize the drift. Figure o shows in diagrammatic fashiona simple and .convenient .means for accomplishing this end. The housing 1 30 1nounted in the verticalgimbal contains the gyroscope rotor, thespinaxisbeing indicated at At one end of this the casing rnaylbe provided with a mounting for a bimetallic strip 132- mounting an'overhanging weight .1 34 and surrounded a heating resistance coil 136 whichais in series with a rheostat Y133 'and a source of current such :55 battery 140. Through the use efathis arrangement, which-is so setithatsome current is required to flow even at thethighestambient'temperatures to eliminate drift changeslin ambient temperature-will result in displaqementofthe weight 134 in the direction of the axis eto provide a torquewhich, bytendingto tilt the gyroscope rotor-:will set up a precessional force suhicient to counterbalance the. drift landtthusserve, at least paitially, to minimize theidrift. Not only is such force set uplby reason ofthe ambient temperature changes, but itmay alsctbe controlled by control or current throughthe .heatin gcoil.

It will be evident that vario-tis changes ,may be made in: specific details of *the apparatus-shown withoutrdeparting from the invention as defined in the following claims.

What is claimed is:

1. In a gyroscope having a rotor housing, and a rotor positionally fixed axially and cross-axially relative to said housing, means for compensating for drift due to changes in ambient temperature comprising a temperature-defiectible element mounted upon said housing and extending therefrom and substantially normal to the spin axis for imparting to the rotor a torque about an axis normal to the spin 2. In a gyroscope having a rotor housing, and a rotor positionally fixed axially and cross-axialiy relative to said housing, means for compensating for drift due to changes in ambient temperature comprning a weighted bimetallic element mounted upon said housing and extending freely therefrom substantially normal to the spin axis for imparting to the rotor a torque about an axis normal to the spin axis.

3. In a gyroscope having a rotor housing, and a rotor positionally fixed axially and cross-axially relative to said housing, means for compensating for drift due to changes in ambient temperature comprising a Weighted bimetallic element mounted upon said housing and extending reely therefrom substantially normal to the spin axis for imparting to the rotor a torque about an axis normal to the spin axis, and controllable means for heating said element.

Reterences Cited in the file of this patent UNITED STATES PATENTS 1,773,172 Davis Aug. 19, 1930 2,384,838 Kellogg Sept. 18, 1945 2,395,940 Ritter Mar. 5, 1946 2,729,63 Dolude Oct. 11, 1955 2,789,436 White Apr. 23, 1957 

